1. Field of the Invention
The invention relates to a probe device for fluid flow investigations, and in particular, to a new traverse probe mechanism for fully three-dimensional flow investigation for subsonic and supersonic applications in turbo-machinery.
2. Description of the Prior Art
It is of interest to investigate the thermodynamic and mechanical behavior of turbo-machinery, such as a low pressure turbine apparatus particularly betwen blade rows. One obvious reason is that the results obtained from such investigations can be used as a verification tool for blade path design programs used in turbine apparatus.
For a complete thermodynamic flow investigation, among other parameters, the static and total pressure distribution, the circumferential and radial components of the flow vector, and temperature distributions along the axial and radial planes of the turbine blade path are required.
Presently, traverse probes are usually of the stem integral cylindrical design, and cannot generate accurate pressure measurements over a wide Mach number range. The present probe for turbine interstage measurements is not adjustable to radial flow angles. Also, the traverse shaft itself of the present probe cannot be positioned accurately, nor circumferentially (pitch) traversed with respect to the flow wakes of a stationary blade row. Accurate three-dimensional traversing must be carried out in order to gain further knowledge of the streamline distribution of the turbine under full and part load conditions. Direct velocity and angle measurements of the absolute flow vector under various conditions are needed, as such measurements will serve to reduce uncertainties in flow parameters, as, for instance, velocities, pressures and radial flow angles, and thus, energy coefficients.
In the prior art, total and static pressure traversing techniques are frequently used in turbine flow investigations. However, for the reason of limited access associated with the usual welded-in-place bushings of small diameter to guide the traverse shaft through several turbine cylinders, wedge probes or similar shaft integral probe heads have been applied. It has often been tried to incorporate measurement of radial flow angles with this technique, but due to the necessity of miniaturization of the sensing head, this was achieved only partially through calibrated fixed position probes.
An ideal probe would indicate the true values of total and static pressure independent of stream Mach numbers, Reynolds numbers or directional flow vector. The ideal probe would also utilize an angularly and radially adjustable probe head to measure both circumferential and polar angles of the fluid flow vector. Any flow component that is not symmetric to the sensing head axis should be eliminated in order not to influence true static pressure readings. All pressure sensing orifices should be located a reasonable distance from supporting structure for true reading of static and total pressures. For probing in pressure gradients, four static orifices should be located on the smallest possible diameter. The probe head support should allow geometrically accurate and repeatable positioning. Shaft bending and vibrational influences should be reduced to a minimum. The traverse probe shaft location should be adjustable in the axial and circumferential direction within at least one stator blade pitch.